Sophie Okonedo and David Harewood's will likely be the more recognizable names of the announced cast for the upcoming BBC Radio 4/Radio 4 Extra adaptation of Neil Gaiman and Lenny Henry's popular BBC sci-fi mini-series Neverwhere.

Sophie Okonedo and David Harewood's will likely be the more recognizable names of the announced cast for the upcoming BBC Radio 4/Radio 4 Extra adaptation of Neil Gaiman and Lenny Henry's popular BBC sci-fi mini-series Neverwhere.

In addition to lead actor James McAvoy, Okonedo and Harewood will be joined by fellow heavy-hitters Benedict Cumberbatch, George Harris, Don Gilet, and Abdul Salis.

Neverwhere's story revolves around Londoner Richard Mayhew, whose life as he knows it ends swiftly -- and somewhat unexpectedly -- when he tries to help a hapless stranger and immediately ceases to exist in the mortal world, joining the citizens of London Below.

Co-creator Gaiman recently revealed via his blog how the project came to be:

"(It'll start on Radio 4 and then go over to Radio 4 extra.) The adaptation is by Dirk Maggs, who did the last three Hitchhiker's Guide Radio adaptations. He's co-directing it with producer Heather Larmour, who is the one who went off and made this happen after a small enthusiastic chat in a London coffee shop much earlier this year -- the kind of conversation that you have that normally just leaves you feeling happy, but doesn't actually turn into anything real. This time it did."